Preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper for easy cleanup.
In a saucepan over medium heat, melt the butter. Add the minced garlic and cook for about 1 minute until fragrant. Stir in the lemon juice and zest, then remove from heat.
In a mixing bowl, toss the halved baby potatoes with olive oil, salt, and pepper. Spread them out on one side of the prepared baking sheet.
On the opposite side of the baking sheet, place the broccoli florets. Drizzle with olive oil, and season with salt and pepper.
Roast the potatoes and broccoli in the preheated oven for about 20 minutes, or until the potatoes are golden and crispy and the broccoli is tender.
During the last 5 minutes of cooking the vegetables, place the salmon fillets on the baking sheet with the broccoli (if there is room, or you can cook them separately in a different pan). Brush the salmon with the lemon butter sauce.
Return the baking sheet to the oven and roast the salmon for 5-7 minutes, or until it flakes easily with a fork and has reached an internal temperature of 145°F (63°C).
Once cooked, remove everything from the oven. Plate the crispy potatoes, roasted broccoli, and salmon. Drizzle any remaining lemon butter sauce over the salmon and garnish with fresh parsley.